1. Technical Field
The present invention relates to an electronic timepiece with an internal antenna.
2. Related Art
Japanese Unexamined Patent Appl. Pub. JP-A-2000-59241 teaches an electronic timepiece with internal antenna that has a ring antenna (dipole antenna) that uses a metal case member as a ground plane. Because the ground plane operates as a reflector in this ring antenna, the ground plane must be sufficiently separated from the antenna electrode on a dielectric. Japanese Unexamined Patent Appl. Pub. JP-A-H07-193416 teaches an electronic timepiece with an internal antenna that houses a slot antenna inside the external case. A slot antenna is an antenna with a slot (slit) in a metal plate.
It may also be desirable to use metal case members for the external case of a wristwatch. While the electronic timepiece with an internal antenna described in JP-A-2000-59241 has a metal case, balancing maintaining reception performance with a small wristwatch size is difficult because the antenna electrode and the ground plane (case member) must be sufficiently separated in order to ensure sufficiently high reception performance. Using a slot antenna is preferable in order to reduce the size while also maintaining reception performance.
The electronic timepiece with an internal antenna taught in JP-A-H07-193416 uses a slot antenna, but cannot receive circularly polarized waves, one example of which are satellite signals from GPS (Global Positioning System) satellites. JP-A-H07-193416 also does not describe a configuration suitable to using an external case made of metal.